Switch travis-ci build to 64 bit ROOT binaries
Switch travis-ci build to 64 bit ROOT binaries

rootpy/root_numpy,rootpy/root_numpy,ndawe/root_numpy,ibab/root_numpy,scikit-hep/root_numpy,ndawe/root_numpy,ndawe/root_numpy,rootpy/root_numpy,scikit-hep/root_numpy,scikit-hep/root_numpy,ibab/root_numpy,ibab/root_numpy,scikit-hep/root_numpy,ibab/root_numpy,rootpy/root_numpy,ndawe/root_numpy